A quarter of the Afghanistan and Iraq war veterans treated with US government-funded health care have been diagnosed with a mental disorder, according to a study published Monday.

And when psychosocial disorders such as domestic violence were included, the number of war veterans suffering from mental illnesses rose to 31 percent.

The instances of mental illness among recently discharged troops and members of the National Guard are significantly higher than those of a study published last year which examined active duty troops, the lead researcher told AFP.

That study found that while a third of returning troops were accessing mental health services, only 12 percent were diagnosed with a mental illness or psychosocial disorder.

"That's a big difference," said Karen Seal, a physician and researcher at the San Francisco Veterans Affairs Medical Center.

Of significant concern was the finding that 56 percent of those diagnosed had more than one mental illness, Seal said.

"When people have more than one diagnosis they become more challenging to diagnose and, more importantly, we believe are more challenging to treat," she explained.

The study comes just days after the Bush administration vowed a "comprehensive review" of veteran care following revelations that soldiers being treated at the renowned Walter Reed Army Medical Center were living in a building with mold-covered walls, infestations of mice and cockroaches, and holes in the ceiling.

That scandal exposed a broader problem with the under-funding of the VA system, said Joe Davis, a spokesman for the Veterans of Foreign Wars.

With a backlog of more than 860,000 medical claims and waiting times of up to a year for treatment, many of the troops coming home are not getting the help they need, Davis said.

And that includes treatment of mental disorders, which are a predictable result of the kinds of stresses troops face under combat, Davis said.

"War changes everybody and everybody is going to have to deal with it in one way or another," Davis said.

"The military is not doing enough on the preventative side or the treatment side because the military's role is to patch them up and send them to the VA. The VA is not doing enough because they did not prepare for the huge influx of new customers coming in from the wars and they haven't budgeted for it."

Early detection and treatment is critical, the study authors wrote, if the military is to prevent chronic mental illness among troops "which threatens to bring the war back home as a costly personal and public health burden."

The results also "signal a need for improvements in the primary prevention of military service-related mental health disorders, particularly among our youngest service members," the authors concluded.

The researchers examined the records of 103,788 veterans of these operations who were first seen at Veterans Affairs facilities between September 30, 2001, and September 30, 2005. About 29 percent of war veterans accessed VA health care facilities, the study found.

The most common diagnosis was post-traumatic stress disorder among 13 percent of troops, followed by anxiety and adjustment disorders among six percent of troops and depression and substance abuse among five percent of troops.

More than half of the troops studied were younger than 30 years of age, 13 percent were women, nearly a third were members of ethnic minority groups and nearly half were veterans of the National Guard or Reserve components, the study found.

The troops most at risk were those aged 18 to 24, the study found, but mental illnesses were common among all subgroups.

The study was published in the Journal of the American Medical Association's Archives of Internal Medicine.